I was very surprised that GCC could optimize NEON SIMD intrinsics. After spending hours trying to optimize my vector code, trying to get the spacing between register dependencies right to reduce stalls, breaking long reduction operations into intermediate results, messing with LLVM-MCA, etc., I realized that I just couldn’t beat the compiler. It was doing its best to allocate registers and reorder instructions to keep the pipeline filled.
I don’t think it always did the best job and saw a bunch of register spills I thought were unnecessary, but I couldn’t justify the time and effort to do it in assembly…
Storage tubes are amazing. I once had a Tektronix 464 scope. Unlike the ubiquitous 465, the 464 was an analog storage oscilloscope! The persistence of the storage tube let you capture pulses, visualize signal jitter, etc. And there was a very satisfying erase button that cleared the tube with the characteristic green flash.
You could also just mess with the horizontal/vertical position knobs and use it as a very expensive Etch-a-Sketch.
Unlike a television CRT, the storage tube will "remember" everywhere the electron beam struck the screen as long as the voltage is below the erase threshold.
What's wild is that this information can be read back out of the device. So, it's not just a display but also memory. It's a destructive reading process (not unlike core memory) where detection is also erasure, but it really is RAM... of a sort.
I have seen these throughout the US and Europe and been fascinated by them. Penn Station has (had? been a while) a big one with more segments per character. I’ve been trying forever to find the name of this particular style of segmented displays and get more info on them. The closest I could find is “mosaic display.”
Love this article!
Signed,
someone who has an obsession with segmented displays
The Penn Station passenger display was, according to the NYT, segmented LCD glass made by Signature Technologies in Arizona.
It had 43 segments (each character had a 13 segment column, 17 segments column, then another 13 segment column that was a mirror of the first). You can see the segment shape on the original sign:
I've done small embedded Linux systems and it makes me so happy that there is a (mostly) compatible implementation built into busybox. svlogd's rotation and size capping makes it great when using limited-lifespan nonvolatile storage like eMMC.
I do the same thing, although as "embedded" systems get bigger I've moved some things over to systemd.
It's a little complicated to set up if your root file system is read-only, since runit really wants to write to the disk, and you must set up symlinks pointing to tmpfs.
I acquired a nonfunctional Diehl VSR a while back, naïvely thinking I could bring it back to life.
Oh my goodness, I took the cover off and what I saw was jaw-dropping. Thousands, possibly tens of thousands, of the most densely packed metal levers and cams and gears one could ever imagine. Nearly all of which would have needed cleaning and lubrication. Getting this thing fully working could have taken a year or more, especially with no repair manuals, and all available information in German.
The respect I have for the designers of these machines, and the servicepeople who repaired them, is immeasurable.
They are also electrical death traps. Lots of exposed switch contacts carrying mains voltage.
I was there when we added it to Preview ;) I think Nils wrote the code to hook it up, because he also worked on the loupe and how it would automatically lock onto the bounding box of a line.
Hi, Matt. Yeah, one of the engineers is on HN from time to time — I thought he might see the post and respond. (Your reminding me of Nils made me smile this morning.)
Ahem. Actually what I am most proud of is that I made pinch to zoom keep characters focussed during zooming. At that time, Safari let things get blurry until the user stopped zooming and then it snapped to focus. That is what I was supposed to do, but I decided to use mipmaps instead.
Surprise no one's mentioned yet that the firmware is written in Rust. As someone who's struggled with getting started with embedded Rust (the landscape seems to be changing quite a lot?) it looks like a good example.
Also it's a bit startling to see floating-point code used so freely. Shows how rapidly the capabilities of MCUs have developed. 15 years ago, doing floating point on a microcontroller would be unspeakable /s
Yeah embassy has improved tons recently. This is because embedded Rust is receiving a lot of investment from industry, embedded engineers desperately want a real C alternative there.
Did this recently for my CoCo 2. Used a mashup of several composite mods floating around (including this one) and built it on a piece of stripboard that fit in the same footprint as the RF modulator. Sourcing the MC1372 was tricky, but NTE makes a replacement, NTE855. I used a 3.5mm TRS jack for the audio/video output so I didn’t have to drill a second hole in the case, and then all you need is a cheap 3.5mm stereo to RCA cable.
Wish I had a schematic but I kinda just wired it freehand.
I don’t think it always did the best job and saw a bunch of register spills I thought were unnecessary, but I couldn’t justify the time and effort to do it in assembly…